Association between mRNA COVID-19 vaccines and Rare Heart Disease
A study published by The BMJ provides an up-to-date summary of evidence on the risk of heart
inflammation (myocarditis and pericarditis) after mRNA vaccination against the COVID-19 virus.
The review of more than 8,000 reported cases from 46 studies by researchers in Canada confirms
previous reports that myocarditis is rare, but cases are highest among young males shortly after a second
dose. It also shows that, while cases are predominantly mild, the risk of myocarditis or pericarditis might
be lower when the second dose is given more than 30 days after the first dose. However, the researchers
warn that, in general, the evidence is of low certainty and say these findings must be considered alongside
the overall benefits of vaccination.
The results show that rates of myocarditis after mRNA vaccines were highest in male adolescents and
young male adults (50-139 cases per million in 12-17 year olds and 28-147 cases per million in 18-29
But they point out that the clinical course of myocarditis in children 5-11 years, after a third dose, and for
those with previous myocarditis after mRNA vaccination is largely unknown. And although the short
term course has consistently shown to be quite mild and self-limiting, they say more data for longer term
prognosis is needed.
As such they conclude: “As the covid-19 pandemic enters its third year, continued surveillance of
myocarditis after mRNA vaccines, especially in younger ages, after dose three (and subsequent doses)
and in previous cases is needed to support continued decision making for covid-19 boosters.”
And they call for additional monitoring of people with relevant underlying conditions, long term follow-
up of patients with myocarditis, and further studies to “enhance understanding of the mechanism or
mechanisms of myocarditis and pericarditis after vaccination.” They point out that key uncertainties
remain, including risks associated with boosters, risks associated with primary vaccination of young
children, and the long-term outcomes of those who experience myocarditis.
“But these uncertainties must be placed in the context of the substantial and widely accepted benefits of
vaccination,” they conclude.